Speed up tasks (#4278)

* fact gathering should run only once per node
* eliminate ansible version check, it is at the beginning of each
  playbook

cluster.yml

@@ -35,13 +35,14 @@
   any_errors_fatal: "{{ any_errors_fatal | default(true) }}"
   vars:
     ansible_ssh_pipelining: true
-  gather_facts: true
+  gather_facts: false
   pre_tasks:
     - name: gather facts from all instances
       setup:
       delegate_to: "{{item}}"
-      delegate_facts: True
+      delegate_facts: true
       with_items: "{{ groups['k8s-cluster'] + groups['etcd'] + groups['calico-rr']|default([]) }}"
+      run_once: true
 
 - hosts: k8s-cluster:etcd:calico-rr
   any_errors_fatal: "{{ any_errors_fatal | default(true) }}"

roles/kubernetes/preinstall/tasks/0020-verify-settings.yml

 ---
-- name: Stop if ansible version is too low
-  assert:
-    that:
-      - ansible_version.full is version('2.3.0', '>=')
-  run_once: yes
-
 - name: Stop if either kube-master, kube-node or etcd is empty
   assert:
     that: groups.get('{{ item }}')